[css-flexbox] Clarify how flex-basis and 'flex basis' interact, and how it becomes 'content'.

Author: tabatkins

css-flexbox/Overview.bs

@@ -1535,11 +1535,12 @@ The 'flex' Shorthand</h3>
 
 		<dt><dfn><<'flex-basis'>></dfn>
 		<dd>
-			This component sets the 'flex-basis' <a href="#flex-components">longhand</a>
-			and specifies the <dfn dfn>flex basis</dfn>:
+			This component sets the 'flex-basis' <a href="#flex-components">longhand</a>,
+			which specifies the <dfn dfn>flex basis</dfn>:
 			the initial <a>main size</a> of the <a>flex item</a>,
 			before free space is distributed according to the flex factors.
-			It accepts the same values as the 'width' and 'height' properties
+
+			<<'flex-basis'>> accepts the same values as the 'width' and 'height' properties
 			(except that ''flex-basis/auto'' is treated differently)
 			plus the ''content'' keyword:
 
@@ -1726,14 +1727,14 @@ The 'flex-basis' property</h4>
 	The 'flex-basis' property sets the <a>flex basis</a>.
 	It accepts the same values as the 'width' and 'height' property, plus ''content''.
 
-
 	For all values other than ''flex-basis/auto'' and ''content'' (defined above),
-	'flex-basis' is resolved the same way as 'width' in horizontal writing modes [[!CSS21]].
+	'flex-basis' is resolved the same way as 'width' in horizontal writing modes [[!CSS21]],
+	except that if a value would resolve to ''width/auto'' for 'width',
+	it instead resolves to ''content'' for 'flex-basis'.
 	For example, percentage values of 'flex-basis' are resolved against
-	the flex item's containing block (i.e. its flex container)
+	the flex item's containing block (i.e. its <a>flex container</a>);
 	and if that containing block's size is <a>indefinite</a>,
-	the result is the same as a <a>main size</a> of <a value for=width>auto</a>
-	(which in this case is treated as ''content'').
+	'flex-basis' becomes ''content''.
 	As another corollary,
 	'flex-basis' determines the size of the content box,
 	unless otherwise specified